CPP device with a plurality of metal oxide templates in a confining current path (CCP) spacer

ABSTRACT

A novel CCP scheme is disclosed for a CPP-GMR sensor in which an amorphous metal/alloy layer such as Hf is inserted between a lower Cu spacer and an oxidizable layer such as Al, Mg, or AlCu prior to performing a pre-ion treatment (PIT) and ion assisted oxidation (IAO) to transform the amorphous layer into a first metal oxide template and the oxidizable layer into a second metal oxide template both having Cu metal paths therein. The amorphous layer promotes smoothness and smaller grain size in the oxidizable layer to minimize variations in the metal paths and thereby improves dR/R, R, and dR uniformity by 50% or more. An amorphous Hf layer may be used without an oxidizable layer, or a thin Cu layer may be inserted in the CCP scheme to form a Hf/PIT/IAO or Hf/Cu/Al/PIT/IAO configuration. A double PIT/IAO process may be used as in Hf/PIT/IAO/Al/PIT/IAO or Hf/PIT/IAO/Hf/PIT/IAO schemes.

FIELD OF THE INVENTION

The invention relates to a high performance magnetic read head elementand a method for making the same, and in particular, to an amorphousmetal layer or amorphous oxide layer that is formed on a copper spacerand subjected to a plasma treatment followed by an ion-assistedoxidation to form a confining current path (CCP) layer between an AP1layer in the pinned layer stack and a free layer and thereby improvecurrent perpendicular to plane (CPP) device uniformity.

BACKGROUND OF THE INVENTION

A CPP-GMR head where GMR refers to a giant magnetoresistive effect isconsidered as one promising sensor to replace the conventional CIP(current in plane) GMR head for over 200 Gb/in² recording density. GMRspin valve stacks typically have a configuration in which twoferromagnetic layers are separated by a non-magnetic conductive layer(spacer). One type of CPP-GMR sensor is called a metallic CPP-GMR thatcan be represented by the following configuration in which the spacerbetween the AP1 pinned layer and free layer is a copper layer and thefollowing layers are sequentially formed on a substrate:Seed/AFM/AP2/Ru/AP1/Cu/free layer/capping layer. One of theferromagnetic layers is a pinned layer in which the magnetizationdirection is fixed by exchange coupling with an adjacentanti-ferromagnetic (AFM) or pinning layer. The pinned layer may have asynthetic anti-parallel (SyAP) structure wherein an outer AP2 layer isseparated from an inner AP1 layer by a coupling layer such as Ru. Thesecond ferromagnetic layer is a free layer in which the magnetizationvector can rotate in response to external magnetic fields. The rotationof magnetization in the free layer relative to the fixed layermagnetization generates a resistance change that is detected as avoltage change when a sense current is passed through the structure. Ina CPP configuration, a sense current is passed through the sensor in adirection perpendicular to the layers in the stack. A lower resistanceis detected when the magnetization directions of the free and pinnedlayers are in a parallel state (“1” memory state) and a higherresistance is noted when they are in an anti-parallel state or “0”memory state.

In a typical CPP-GMR sensor, a bottom synthetic spin valve film stackwhich is generally represented as [seed/AFM/pinned/spacer/free/cap] isemployed for biasing reasons and a CoFe/NiFe composite free layer isconventionally used following the tradition of CIP-GMR technology.

Ultra-high density (over 100 Gb/in²) recording requires a highlysensitive read head. To meet this requirement, the CPP configuration isa stronger candidate than the CIP configuration which has been used inrecent hard disk drives (HDDs). The CPP configuration is more desirablefor ultra-high density applications because a stronger output signal isachieved as the sensor size decreases, and the magnetoresistive (MR)ratio is higher for a CPP configuration. An important characteristic ofa GMR head is the MR ratio which is dR/R where dR is the change inresistance of the spin valve sensor and R is the resistance of the spinvalve sensor before the change. A higher MR ratio is desired forimproved sensitivity in the device and this result is achieved whenelectrons in the sense current spend more time within the magneticallyactive layers of the sensor. Interfacial scattering which is thespecular reflection of electrons at the interfaces between layers in thesensor stack can improve the MR ratio and increase sensitivity.Unfortunately, the MR ratio is often very low (<5%) in many CPP-GMR spinvalve structures involving metal spacers. A MR ratio of ≧10% and an RAof <0.5 ohm-um² are desirable for advanced applications.

Another type of sensor is a so-called confining current path (CCP) CPPGMR sensor where the current through the Cu spacer is limited by themeans of segregating metal path and oxide formation. With a CCP-CPPscheme, the Cu metal path is limited through an insulator template sothat the MR ratio can be enhanced quite significantly. An example of aCCP-CPP GMR sensor has the following configuration:Seed/AFM/AP2/Ru/AP1/Cu/CCP layer/Cu/free layer/capping layer where theCCP layer is sandwiched between two copper layers. Typically, a CCPlayer is formed by first growing an Al or AlCu layer on a Cu layer atthe top of a crystalline stack of layers which results in rough surfacemorphology and large grain size with large distributions in the Al orAlCu film. In the ensuing pre-ion treatment (PIT) and ion-assistedoxidation (IAO) steps where Al or AlCu is exposed to oxygen to form acurrent confining path through Al₂O₃ and Cu segregation, it isinevitable that a rugged Al or AlCu layer leads to a non-uniform AlOxlayer which means poor uniformity and a loss of control in deviceperformance.

CCP layer formation is based on a well known fact that Al atoms have adifferent (higher) mobility than Cu atoms. After the PIT treatment, Aland Cu start to segregate from each other and when exposed to oxygenduring the IAO step, Al attracts oxygen to form amorphous AlOx. BecauseCu is more chemically inert to oxygen than Al under the processconditions, it tends to remain as a Cu metal phase and eventually formsa metal path.

In order for the CCP-CPP GMR approach to be widely accepted inmanufacturing, a smoother CCP forming layer and one that has amorphology which enables more uniform metal paths to be formed duringthe PIT/IAO processes is required so that significant improvement indevice uniformity can be achieved. A CCP forming layer is defined hereas the one or more layers deposited on a Cu spacer which aresubsequently transformed (with Cu) into the actual CCP layer as a resultof the PIT and IAO processes.

During a routine search of the prior art, the following references werefound. In U.S. Pat. No. 7,177,121, an amorphous metal layer made of anoxidized NiCr alloy or oxidized CoCr alloy is formed on the sides of amagnetoresistive element and beneath a magnetic domain control film, themagnetic characteristics of the magnetic domain control film areimproved.

U.S. Patent Application Publication No. 2005/0094317 discloses acomposite layer in a MTJ stack that is comprised of a central currentcontrol region and an insulating layer on either side of the centralregion. The central current control region is made of an oxide, nitride,or oxynitride of at least one of B, Si, Ge, Ta, W, Nb, Al, Mo, P, V, As,Sb, Zr, Ti, Zn, Pb, Th, Be, Cd, Sc, Y, Cr, Sn, Ga, In, Rh, Pd, Mg, Li,Ba, Ca, Sr, Mn, Fe, Co, Ni, Rb, and rare earth metals and may containone type of metal such as Cu, Au, Ag, Pt, Pd, Ir, and Os.

U.S. Patent Application Publication No. 2003/0053269 describes a currentconfining layer made of Al₂O₃ or TaO₂ that is formed between a pinnedlayer and a free layer.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a CCP forming layerconfiguration during fabrication of a CPP device that promotes asmoother surface morphology as well as a smaller and more uniform grainsize in the oxidizable portion of the CCP forming layer prior to the PITand IAO processes.

A further objective of the present invention is to form metal oxidetemplates with improved uniformity during CPP device fabrication suchthat the Cu metal paths formed therein are more uniform than in aconventional CCP scheme involving segregated Cu metal paths in AlOxtemplates and thereby improve dR/R, dR, and R uniformity across thewafer.

These objectives are achieved according to the present invention byfirst providing a substrate on which a CPP-GMR sensor (CPP element) isto be fabricated. In one embodiment, the substrate is a bottom shield ina GMR read head and a CPP stack of layers having a bottom spin valveconfiguration is formed on the substrate by sequentially forming a seedlayer, AFM layer, synthetic anti-parallel (SyAP) pinned layer, Cu spacerwith CCP layer therein, free layer, and a cap layer in a sputterdeposition system. Formation of the CCP layer is achieved by firstdepositing a CCP forming layer on a lower portion of the Cu spacer. Akey feature is that the CCP forming layer is comprised of at least oneamorphous layer made of metal, an alloy, or an oxide, and, in someembodiments has an oxidizable layer made of Al, AlCu, Mg, MgCu, Ti, Cr,Zr, Ta, Hf, Fe, or the like, or an alloy from one of the aforementionedelements. The amorphous layer is preferably Hf but also may be made ofZr, CoFeB, Ta, Nb, or the like. The amorphous layer will be oxidized toan oxide layer and its primary purpose is to provide a small grain sizewith smooth surfaces that (a) promotes more uniform Cu paths formed in ametal oxide template derived from the amorphous layer, and (b) improvesthe oxidizable layer surface morphology and reduces grain size and sizedistribution therein so that a more uniform metal oxide template derivedfrom the overlying oxidizable layer is formed following plasma treatmentand oxidation processes. One or more layers in the CCP forming layer issubjected to a PIT/IAO process sequence involving pre-ion treatment(PIT) followed by an ion-assisted oxidation (IAO), plasma oxidation, orradical oxidation step to transform the CCP forming layer and at least aportion of the Cu spacer into a CCP layer having one or more metal oxidetemplates with segregated Cu metal paths therein. Thereafter an upperportion of the copper spacer is deposited on the CCP layer to provide aCCP spacer represented by Cu/CCP layer/Cu.

In one aspect, the CCP scheme disclosed in the first embodiment may berepresented by A/X/PIT/IAO where A is the amorphous layer made of metal,alloy, or oxide, and X is the oxidizable metal layer. PIT/IAO indicatesthat the A/X composite structure (CCP forming layer) was treated with aPIT step followed by an IAO step to form a first metal oxide templatefrom the amorphous layer and a second metal oxide template from theoxidizable metal layer, both having segregated Cu metal paths therein.The first metal oxide template contacts the lower portion of the Cuspacer while the second metal oxide template contacts the upper portionof the Cu spacer. There may be some intermixing of first metal oxidetemplate with the second metal oxide template. The first embodiment alsoencompasses an A/X/A/PIT/IAO configuration in which a second amorphouslayer is deposited on the oxidizable metal layer before the PIT and IAOsequence is performed. In this case, a second metal oxide templatederived from the “X” layer is formed between first and third metal oxidetemplates that are derived from the first and second amorphous metal oralloy layers, respectively. The present invention also provides for anA/PIT/IAO/X/PIT/IAO configuration where the A layer is subjected to thePIT and IAO treatments before the X layer is deposited and treated withthe PIT and IAO steps.

In a second embodiment, the amorphous layer is employed as a CCP forminglayer on the lower Cu spacer layer, and the oxidizable X layer isomitted. This configuration is represented by A/PIT/IAO. Alternatively,a double A layer configuration represented by A/PIT/IAO/A/PIT/IAO may beemployed wherein a first A layer formed on the lower portion of the Cuspacer is treated with the PIT and IAO steps before a second A layer isdeposited on the resulting metal oxide template and is subjected to thePIT/IAO sequence. The A/PIT/IAO/A/PIT/IAO CCP configuration can lead toimproved uniformity because of more uniform oxidation at the top surfaceand via the grain boundaries in the “A” layers. In the secondembodiment, the one or more A layers are transformed into a single metaloxide template with segregated Cu metal paths formed therein when thefirst and second A layers are comprised of the same metal or alloy. Inone aspect, the first A layer may be made of a different metal or alloythan the second A layer thereby producing a second metal oxide templateon the first metal oxide template.

There is a third embodiment similar to the second embodiment except athin Cu layer is inserted between the two A layers. This configurationis represented by N/PIT/IAO/Cu/A/PIT/IAO. In this case, a Cu layer isdeposited on the first metal oxide template generated by performing PITand IAO processes on the first A layer. Then a second A layer isdeposited on the Cu layer and PIT and IAO processes are performed asecond time to produce a second metal oxide template on the first metaloxide template. In one aspect, the same metal or alloy is employed inboth the first and second A layers to give essentially a single CCPlayer having a metal oxide template and Cu metal paths therein. However,the first A layer may be comprised of a different metal or alloy thanthe second layer which would result in a composite CCP structure wherethe first metal oxide template derived from the first A layer isdifferent than the second metal oxide template formed from the second Alayer. Thereafter, the upper portion of the Cu spacer is deposited onthe second metal oxide template to form a CCP spacer having a Cu/CCPlayer/Cu configuration. Optionally, the third embodiment may have anA/Cu/A/PIT/IAO configuration in which a thin Cu layer is deposited onthe first A layer followed by deposition of the second A layer on thethin Cu layer before the PIT and IAO steps are performed.

In a fourth embodiment, the CCP configuration of the first embodiment ismodified by inserting a thin Cu layer between the A layer and the Xlayer as in A/Cu/X/PIT/IAO. Alternatively, the A layer may be subjectedto PIT and IAO process steps before a Cu layer is deposited on theresulting first metal oxide template derived from the A layer. Then theX layer is deposited on the thin Cu layer followed by PIT and IAOprocess steps to generate a second metal oxide template on the firstmetal oxide template in which both metal oxide templates have Cu pathstherein. This scheme is represented by A/PIT/IAO/Cu/X/PIT/IAO.

The present invention also encompasses a method of forming the CPP-GMRelement comprised of the aforementioned Cu/CCP layer/Cu spacerconfigurations. All layers in the CPP-GMR element are preferably formedin a sputter deposition system that includes one or more sputterdeposition chambers and at least one oxidation chamber. The PIT processmay be performed in a sputter deposition chamber followed by an IAOprocess in an oxidation chamber of a sputter deposition mainframe. Afterall layers in the CPP-GMR element are laid down on the substrate, aconventional patterning and etching sequence may then be followed todefine the shape of the CPP-GMR element. Subsequently, a dielectriclayer and a hard bias layer may be formed adjacent to the sidewalls ofthe CPP-GMR element in the CCP-CPP GMR sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a CPP-GMR sensor with a stack oflayers in which a confining current path (CCP) spacer is formed betweenan AP1 pinned layer and the free layer according to one embodiment ofthe present invention.

FIG. 2 is a cross-sectional view of a read head comprised of a CPP-GMRsensor according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a confining current path scheme for a CCPspacer between a pinned layer and a free layer in a magnetoresistiveelement such as a CPP-GMR sensor. The drawings are provided by way ofexample and are not intended to limit the scope of the invention.Although the exemplary embodiments describe a bottom spin valvestructure, the confining current path scheme of the present inventionmay also be employed in a top spin valve structure or a multilayer spinvalve configuration in a CPP-GMR element as appreciated by those skilledin the art. The present invention is also a method of making a CCP-CPPGMR sensor with improved uniformity compared with a conventional CCP-CPPGMR design involving Cu paths in a metal oxide template. The terms“device”, “sensor”, and “element” may be used interchangeably.

It is well known in conventional CCP schemes that the top surface of anoxidizable Al or AlCu layer formed on a Cu spacer is rough prior to thePIT and IAO process sequence. Furthermore, when the Al or AlCu layer isoxidized to form AlOx templates for the Cu metal paths, the volume ofthe CCP layer may expand by as much as 30% which increases surfaceroughness on the metal oxide template. Since the Cu metal paths areformed through the grain boundaries of the rough AlOx templates, the Cumetal paths have a large variation in terms of width and length therebyleading to large variations in RA and dR/R for the plurality of sensordevices fabricated across the wafer. The inventors have discovered thatby first depositing an amorphous layer made of metal, alloy, or oxide onthe Cu spacer, the overlying oxidizable portion of the CCP forming layerwill have a smoother surface and smaller grain size to promote moreuniform Cu metal paths in the resulting metal oxide template followingthe PIT and IAO process steps. Moreover, an amorphous layer made ofmetal or alloy that is oxidizable and formed on a Cu spacer may beemployed without an overlying oxidizable layer in a CCP scheme withsimilar improvement in device uniformity.

Referring to FIG. 1, one embodiment of the present invention is shownthat relates to a CCP-CPP GMR sensor 1 having a bottom spin valvestructure. The view in FIG. 1 is from a cross-section along an airbearing surface (ABS) in the read head. A substrate 8 is shown that maybe a first magnetic shield (S1) in a read head. For example, thesubstrate 8 may be comprised of a 2 micron thick layer of anelectroplated permalloy. There is a seed layer 9 that may be comprisedof a lower Ta layer and an upper Ru layer (not shown) formed on thesubstrate 8. The seed layer 9 promotes a smooth and uniform crystalstructure in the overlying AFM and pinned layers that enhances the MRratio in the CCP-CPP GMR sensor 1.

An AFM layer 10 is formed on the seed layer 9 and is preferablycomprised of IrMn having a composition of about 18 to 22 atomic % Ir anda thickness of about 50 to 75 Angstroms. Alternatively, the AFM layer 10may be made of MnPt having a composition between about 55 to 65 atomic %manganese and with a thickness of about 125 to 175 Angstroms. Thoseskilled in the art will appreciate that other materials such as NiMn,OsMn, RuMn, RhMn, PdMn, RuRhMn, or PtPdMn may also be employed as theAFM layer 10 which is used to pin the magnetization direction in anoverlying ferromagnetic (pinned) layer 14.

There is a synthetic anti-parallel (SyAP) pinned layer 14 formed on theAFM layer 10 that preferably has an AP2/coupling layer/AP1configuration. The AP2 layer 11 in the pinned layer may be comprised ofCoFe with a composition of about 75 to 90 atomic % cobalt and athickness of about 20 to 50 Angstroms and is formed on the AFM layer 10.The magnetic moment of the AP2 layer 11 is pinned in a directionanti-parallel to the magnetic moment of the AP1 layer 13. For example,the AP2 layer may have a magnetic moment oriented along the “+x”direction while the AP1 layer has a magnetic moment in the “−x”direction. The AP2 layer 11 may be slightly thicker than the AP1 layerto produce a small net magnetic moment for the pinned layer 14. Exchangecoupling between the AP2 layer 11 and the AP1 layer 13 is facilitated bya coupling layer 12 that is preferably comprised of Ru with a thicknessof about 7.5 Angstroms. Optionally, Rh or Ir may be employed as thecoupling layer 12.

The AP1 layer 13 may be a composite with a [CoFe/Cu]_(k)/CoFeconfiguration wherein k=1, 2, or 3. In an embodiment where k=1, the AP1layer 13 may be comprised of a stack wherein the first and third layers(not shown) are made of CoFe with a Fe content of 50 to 90 atomic % anda thickness between 10 and 20 Angstroms, and preferably 18 Angstroms,and the second (middle) layer is made of Cu with a thickness of 0.5 to 4Angstroms and preferably 2 Angstroms. The use of a laminated AP1 layerto improve CPP-GMR properties is well known in the art. All of the CoFeand Cu layers in the AP1 layer 13 have a magnetic moment in the “−x”direction when the AP1 layer has a magnetic moment along the “−x” axisin the exemplary embodiment. Optionally, the AP1 layer 13 may be made ofCoFe or a composite comprised of CoFe and CoFeB.

A key feature of the present invention is a CCP spacer 18 formed on theAP1 layer 13. The CCP spacer 18 is a composite comprised of a confiningcurrent path (CCP) layer sandwiched between two Cu layers 15, 17 eachhaving a thickness from 0 to about 10 Angstroms. It should be understoodthat the first step in forming the CCP spacer 18 is depositing a firstCu layer 15 on the AP1 layer 13. Alternatively, in a top spin valve, theCCP spacer 18 may be formed on a free layer. In a first embodiment, aCCP forming layer (not shown) is formed on the first Cu layer 15 and iscomprised of at least one amorphous layer made of a metal, alloy, or anoxide and hereafter referred to as the “A” layer, and an oxidizablelayer comprised of Al, AlCu, Mg, MgCu, Ti, Cr, Zr, Ta, Hf, Fe, or thelike, or an alloy from one of the aforementioned elements and hereafterreferred to as the “X” layer. The A layer made of metal or alloy has athickness from 1 to 15 Angstroms while the X layer has a thickness fromabout 1 to 15 Angstroms. When the A layer is an amorphous oxide, thepreferred thickness is less than 15 Angstroms.

In one aspect, the X layer is formed above the A layer. The A layer maybe made of Hf, Zr, CoFeB, Ta, Nb, Ti, or B for example, and serves topromote a smoother surface morphology and smaller grain size in anoverlying X layer. Thus, in a subsequent process sequence involving PITand IAO steps, the metal oxide template resulting from oxidation of theX layer will have a smoother surface texture and the Cu metal pathsformed at the grain boundaries will have improved uniformity comparedwith the Cu metal paths formed within typical AlOx templates.Preferably, the A layer is also oxidizable and is believed to form anoxide template with Cu metal paths therein. The amorphous nature of theA layer means the small grain size and smooth surfaces in the A layerpromote the formation of uniform Cu metal paths therein in subsequentPIT and IAO processing. There may be a gradual transition from a metaloxide template made of essentially oxidized A layer near the interfacewith the first Cu layer 15 to a metal oxide template made of essentiallyoxidized X layer at the top of the CCP layer 16 following the PIT/IAOsteps. Thereafter, a second Cu layer 17 is deposited on the CCP layer 16to complete the CCP spacer 18. It should be understood that at least aportion of the first Cu layer 15 reacts to form the Cu paths in themetal oxide templates. Preferably, a portion of the first Cu layer 15remains on the AP1 layer 13 following the IAO process to serve as anoxygen barrier so that the magnetic material in the AP1 layer is notoxidized which could lower the MR ratio and otherwise degrade theperformance of the CCP-CPP GMR sensor 1.

The CCP forming layer in the first embodiment may be represented by anA/X/PIT/IAO configuration which indicates the A layer is formed on thefirst Cu spacer layer 15 and the X layer is deposited on the A layerprior to performing the PIT and IAO processes. During the PIT/IAOprocesses, the CCP forming layer and a portion of the first Cu layer 15are transformed into the CCP layer 16. In one aspect, the lower Cu layer15 is about 2 to 8 Angstroms thick and preferably 5.2 Angstroms thick,and the upper Cu layer 17 has a thickness between 2 and 6 Angstroms andis preferably 3 Angstroms thick. The first metal oxide template in theCCP layer 16 may have a thickness of 2 to 15 Angstroms and the secondmetal oxide template may have a thickness of 2 to 15 Angstroms.

A typical PIT process is performed in a sputter deposition chamberwithin a sputter deposition mainframe that preferably contains at leastone sputter deposition chamber and at least one oxidation chamber. Oneexample of a PIT process employed by the inventors comprises a RF powerof 5 to 200 Watts and an Ar flow of 10 to 200 standard cubic centimetersper minute (sccm) for 5 to 200 seconds. The IAO process may be performedin an oxidation chamber of a sputter deposition mainframe and may becomprised of an Ar flow rate of 5 to 200 sccm, an oxygen flow rate of0.01 to 100 sccm, and a RF power of 5 to 200 Watts for 5 to 2000seconds.

The first embodiment also encompasses an A/X/A/PIT/IAO configuration inwhich a second amorphous (A) layer is deposited on the X layer beforethe PIT and IAO sequence is performed. For example, when A is Hf and Xis Mg, then a first hafnium oxide template is formed on the first Culayer 15 and a MgO template is formed on the first hafnium oxidetemplate. There is also a second hafnium oxide template formed on theMgO template with segregated Cu metal paths formed within each of thethree aforementioned metal oxide templates. Optionally, the amorphousmetal or amorphous alloy selected for the second A layer may bedifferent than the material in the first A layer. As a result, each ofthe three metal oxide templates in the CCP layer 16 may be comprised ofa different metal and has a thickness of 1 to 15 Angstroms. It should beunderstood that the boundaries between adjacent metal oxide layers maynot be clearly defined since some intermixing of metal oxide templatescan occur during the PIT and IAO processes. Furthermore, the Cu densityin the second and third metal oxide templates may be less than in thefirst metal oxide template since the Cu must migrate a greater distanceto reach the second and third metal oxide templates.

The first embodiment also provides for an A/PIT/IAO/X/PIT/IAOconfiguration where the A layer is subjected to the PIT and IAOtreatments before the X layer is deposited and treated with the PIT andIAO steps. In this case, a first metal oxide template made of oxidized Alayer is formed on the first Cu layer 15 and a second metal oxidetemplate made of oxidized X layer is formed on the first metal oxidetemplate. The concentration of metal paths formed in the first metaltemplate may be greater than in the second metal oxide template since Cufrom the lower Cu layer 15 must migrate a larger distance to reach thesecond metal oxide template.

In another aspect, the X layer may be formed on the lower Cu layer 15followed by deposition of the A layer on the X layer. Thus, the firstembodiment also encompasses an X/A/PIT/IAO configuration in which anamorphous A layer is deposited on the X layer before the PIT and IAOprocesses are performed. For example, a Mg/Hf/PIT/IAO configuration maybe used to form a MgO template on the lower Cu layer 15 and a hafniumoxide template on the MgO template. As a result of the PIT/IAO sequence,both metal oxide templates contain Cu metal paths. Thereafter, the upperCu layer 17 is deposited on the resulting CCP layer 16.

In a second embodiment, at least one A layer is employed and the X layeris omitted in the CCP forming layer. This configuration may berepresented by A/PIT/IAO. The A layer formed on the first Cu layer 15 istreated with PIT and IAO processes to form a metal oxide template withCu metal paths therein to produce a CCP layer 16 having a thickness ofabout 5 to 25 Angstroms on the remaining portion of first Cu layer 15.An important requirement for formation of a segregated Cu metal path ina metal oxide template is that the metal should be more readily oxidizedthan Cu and should have a different mobility than Cu. Preferably, the Alayer metal or alloy has a higher mobility than Cu, but in principle, anA layer material that has a lower mobility than Cu is also acceptable.Thereafter, the second Cu layer 17 is deposited on the CCP layer 16.

Alternatively, a double A layer configuration represented byA/PIT/IAO/A/PIT/IAO may be employed wherein a first A layer (not shown)formed on the first Cu layer 15 is treated with the PIT and IAO steps toform a first metal oxide template before a second A layer is depositedon the first metal oxide template having segregated Cu metal pathstherein and is subjected to the PIT/IAO sequence to form a second metaloxide template having segregated Cu metal paths therein. When the firstA layer is comprised of the same material as in the second A layer, thenthe resulting CCP layer 16 has essentially the same metal oxidecomposition throughout. Depending on the thicknesses of the two Alayers, a lower portion of the CCP layer 16 may have a higherconcentration of Cu metal paths than an upper portion because the firstA layer is closer to the first Cu layer 15 during the PIT/IAO sequence.The A/PIT/IAO/A/PIT/IAO CCP configuration can lead to improveduniformity because of more uniform oxidation at the top surface and viathe grain boundaries in the two A layers. It should be understood thatthe second A layer may be made of a different amorphous material than inthe first A layer. The first metal oxide template has a thickness of 2to 15 Angstroms and the second metal oxide template has a thickness of 2to 15 Angstroms.

There is a third embodiment similar to the second embodiment except athin Cu layer (not shown) is inserted between the two A layers. The thinCu layer has a thickness from 0 to 6 Angstroms and preferably less than3 Angstroms. This configuration may be represented byA/PIT/IAO/Cu/A/PIT/IAO. In this case, a thin Cu layer is deposited onthe first metal oxide template generated by performing PIT and IAOprocesses on the first A layer. Then a second A layer is deposited onthe thin Cu layer and PIT and IAO processes are performed a second timeto produce a second metal oxide template on the first metal oxidetemplate. In one aspect, the same metal or alloy is employed in both thefirst and second A layers to give a CCP layer 16 having essentially asingle metal oxide template and Cu metal paths therein. However, thefirst A layer may be comprised of a different metal or alloy than thesecond A layer which would result in a composite CCP structure where thefirst metal oxide template in a lower portion of the CCP layer 16 isdifferent than the second metal oxide template in an upper portion ofthe CCP layer. Thereafter, the upper portion of the Cu spacer isdeposited on the CCP layer 16 to complete the CCP spacer 18. Optionally,the third embodiment may have a A/Cu/A/PIT/IAO configuration in which athin Cu layer is deposited on the first A layer followed by depositionof the second A layer on the thin Cu layer before the PIT and IAO stepsare performed. This configuration is believed to generate a CCP layer 16having a more uniform Cu metal path distribution throughout since the Cuused to form metal paths in the second metal oxide template does notneed to migrate through the first A layer.

In a fourth embodiment, the CCP configuration of the first embodiment ismodified by inserting a thin Cu layer from 0 to 6 Angstroms thickbetween the A layer and the X layer to give an A/Cu/X/PIT/IAO scheme. Inthis case, the CCP layer 16 is comprised of a first metal oxide templateformed from the A layer and a second metal oxide template formed fromthe X layer as a result of the PIT and IAO process sequence.Alternatively, the A layer may be subjected to PIT and IAO process stepsbefore a thin Cu layer is deposited on the resulting first metal oxidetemplate made from the A layer. Then the X layer is deposited on thethin Cu layer followed by PIT and IAO process steps to generate a secondmetal oxide template on the first metal oxide template wherein bothmetal oxide templates have Cu metal paths formed therein. This scheme isrepresented by A/PIT/IAO/Cu/X/PIT/IAO. In this example, the first metaloxide template in the CCP layer 16 has a different composition than thesecond metal oxide template.

Above the CCP spacer 18 is a free layer 19 that may be comprised ofCoFe. Alternatively, the free layer 19 may be a composite in which abottom layer made of CoFe is formed on the CCP spacer 18 and a NiFelayer is disposed on the CoFe layer. The present invention alsoanticipates that other soft magnetic materials may be employed as thefree layer 19 in the GMR-CPP sensor 1.

At the top of the CPP-GMR sensor stack is a cap layer 20 that may be acomposite comprised of a lower Ru layer on the free layer 19 and a Talayer on the Ru layer. Optionally, the cap layer 20 may be comprised ofa composite such as Ru/Ta/Ru or other suitable capping layer materialsused by those skilled in the art.

All of the layers in the CPP stack in CCP-CPP GMR sensor 1 may be laiddown in a sputter deposition system. For instance, the CPP-GMR stack oflayers may be formed in an Anelva C-7100 thin film sputtering system orthe like which typically includes three physical vapor deposition (PVD)chambers each having 5 targets, an oxidation chamber, and a sputteretching chamber. At least one of the PVD chambers is capable ofco-sputtering. Typically, the sputter deposition process involves anargon sputter gas and the targets are made of metal or alloys to bedeposited on a substrate. All of the CPP layers may be formed after asingle pump down of the sputter system to enhance throughput.

The present invention also encompasses an annealing step after all ofthe CPP-GMR layers have been deposited. For example, the CPP-GMR stackcomprised of seed layer 9, AFM layer 10, pinned layer 14, CCP spacer 18,free layer 19, and cap layer 20 may be annealed by applying a magneticfield of about 10K Oe in magnitude along a certain axis for about 0.5 to20 hours at a temperature between 250° C. and 350° C. The annealingprocess may also comprise an annealing step along a hard axis and anannealing step along an easy axis.

Referring to FIG. 2, a CCP-CPP GMR head 30 having a CPP-GMR elementcomprised of layers 9-20 and with sidewalls 21 and a top surface 20 amay be fabricated by coating and patterning a photoresist layer (notshown) on the cap layer surface 20 a after all of the layers in theCPP-GMR stack are deposited. The photoresist layer serves as an etchmask during an ion beam etch (IBE) or reactive ion etch (RIE) sequencethat transfers the pattern through the CPP-GMR stack of layers to formthe sidewalls 21 that are typically sloped so that the top surface 20 ahas a smaller width along the x-axis than that of the seed layer 9. Oncethe etch sequence is complete, the photoresist layer may be removed by aconventional stripping process known to those skilled in the art.

Thereafter, a first dielectric layer 22 made of Al₂O₃ or the like with athickness of about 100 to 150 Angstroms is deposited on the bottomshield 8 and along the sidewalls 21 of the CPP-GMR element by a chemicalvapor deposition (CVD) or physical vapor deposition (PVD) method.Optionally, a seed layer (not shown) such as TiW, Cr, CrTi, or CrMo maybe formed on the first dielectric layer. Next, a hard bias layer 23 thatmay be comprised of CoCrPt or FePt is deposited on the first dielectriclayer 22 (or seed layer) by an ion beam deposition (IBD) or PVD process.In an alternative embodiment, a soft magnetic underlayer such as NiFe,CoFe, CoNiFe, FeTaN, or FeAIN is formed on a seed layer to promote goodlattice matching between the seed layer and hard bias layer 23. Then asecond dielectric layer 24 is deposited on the first dielectric layer 22and on the hard bias layer 23 with a CVD or PVD method, for example. Inone embodiment, the hard bias layer 23 has a thickness of about 200 to400 Angstroms and the second dielectric layer 24 has a thickness betweenabout 150 and 250 Angstroms. A planarization step such as a chemicalmechanical polish (CMP) process may be employed to make the seconddielectric layer 24 coplanar with the top surface 20 a of the cap layer20. An upper shield 25 is disposed on the top surface 20 a of the caplayer 20 and on the second dielectric layer 24. The upper shield 25 maybe a composite layer such as Ta/NiFe as appreciated by those skilled inthe art.

The advantages of incorporating a CCP layer 16 as described hereinwithin a CCP spacer in a CPP GMR sensor are improved dR/R, dR, and Runiformity over CCP schemes involving conventional metal oxide templateswith segregated Cu metal paths. Moreover, the amorphous layer insertedinto the CCP forming layer is believed to minimize the threat of oxygendiffusion from the metal oxide template derived from the oxidizablemetal into the AP1 layer and thereby avoids degradation in sensorperformance. Several examples of CCP configurations in accordance withthe present invention are described below.

COMPARATIVE EXAMPLE 1

An experiment was conducted to demonstrate the improved performance of aCPP-GMR stack of layers comprised of a seed layer, IrMn AFM layer, SyAPpinned layer, CCP spacer of the present invention, free layer, and caplayer that were sequentially formed on a AlTiC substrate. In thisexample, the seed layer has a 10 Angstrom thick Ta lower layer and a 10Angstrom thick Ru upper layer, the IrMn AFM layer has a thickness of 70Angstroms, the AP2 trilayer has a Fe₁₀Co₉₀/Fe₇₀Co₃₀/Fe₁₀Co₉₀configuration, the AP1 layer is a Fe₇₀Co₃₀/Cu/Fe₇₀Co₃₀ laminate, thefree layer is a Fe₂₅Co₇₅/CoFeB/Ni₉₀Fe₁₀ composite, and the cap layer hasa Ru/Ta/Ru configuration. The value next to each layer in the referenceconfiguration below indicates the film thickness in Angstroms. Thereference sample labeled BTF2B3N has a CCP layer with AlOx and Cu metalpaths therein and is formed by treating a Cu/Al/PIT/IAO configurationwith a PIT process comprised of a RF power of 20 Watts and an Ar flowrate of 50 sccm for 35 seconds, and an IAO process comprised of a RFpower of 27 Watts, an Ar flow rate of 35 sccm and an oxygen flow rate of0.56 sccm for 40 seconds. The uniformity data for the reference CCP-CPPGMR sensor structure represented byTa10/Ru10/lrMn70/Fe₁₀Co₉₀8/Fe₇₀Co₃₀10.5/Fe₁₀Co₉₀16/Ru7.5/Fe₇₀Co₃₀12/Cu2/Fe₇₀Co₃₀12/Cu5.2/AlCu8.6/PIT/IAO/Cu3/Fe₂₅CO₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30is provided in Table 1.

TABLE 1 dR/R, dR, and R uniformity data for various device sizes forBTF2B3N under a conventional PIT/IAO process dR/R dR BTF2B3N UniformityUniformity R Uniformity device size FLL Area (%) (%) (%) 2B 0.61 0.28811.232 25.323 15.679 2A 0.49 0.189 8.658 22.605 16.747 1D 0.80 0.51512.062 23.766 13.726 1C 0.37 0.105 9.031 26.497 19.982 1B 0.30 0.0737.437 26.446 20.916 1A & 2C 0.24 0.047 8.814 23.631 22.290

Typically, the 1 sigma uniformity data across the wafer ranges from 7%to 15% for dR/R, 20% to 30% for dR, and 15% to 30% for R. These largevalues for conventional CCP schemes are due to large variations in Cumetal paths formed within the rugged and non-uniform aluminum oxidetemplates generated during the PIT/IAO processes.

The inventors have achieved a substantial improvement in uniformity byinserting an amorphous layer (Hf) between a lower Cu spacer and anoxidizable Al layer in a CCP scheme represented by A/X/PIT/IAO whereA=Hf and X=Al according to one embodiment of the present invention. Inother words, a thin amorphous Hf layer is deposited on the lower Cuspacer before an Al layer is grown. The same PIT and IAO processconditions were employed as in the reference to form a CCP layer. TheCCP-CPP GMR sensor (BTF3A0) with improved uniformity fabricated from aCCP forming layer configuration Hf/Al/PIT/IAO is represented byTa10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀Co₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/A17/PIT/IAO/Cu3/Fe₂₅CO₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.Results are shown in Table 2. Note that dR/R, R, and dR one sigmauniformity are reduced by 50% or more for all device sizes compared withthe reference data in Table 1.

TABLE 2 dR/R, dR, and R uniformity data for various device sizes forBTF3A0 under the new CCP scheme with amorphous layer insertion beforePIT/IAO processing. dR/R dR BTF3A0 Uniformity Uniformity R Uniformitydevice size FLL Area (%) (%) (%) 2B 0.61 0.288 4.370 6.687 6.439 2A 0.490.189 4.350 7.401 3.574 1D 0.80 0.515 3.048 3.382 4.761 1C 0.37 0.1054.466 8.551 4.486 1B 0.30 0.073 3.916 10.564 7.597 1A & 2C 0.24 0.0474.781 10.847 6.848

In another example that represents an A/X/A/PIT/IAO CCP scheme, aCCP-CPP GMR sensor (BTF3FG) was formed with the following structure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀Co₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀CO₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/A12/Hf3/PIT/IAO/Cu3/Fe₂₅Co₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.In this embodiment, a first Hf layer is deposited on a lower Cu spacerfollowed by deposition of an Al layer and then a second Hf layer beforethe PIT/IAO sequence is performed. An upper Cu spacer is deposited onthe resulting CCP layer having a stack of three metal oxide templatesbefore the free layer is formed. In another example that represents anA/X/A/PIT/IAO CCP scheme where Al is replaced by Mg as the oxidizable“X” layer, a CCP-CPP GMR sensor (BTF39J) was formed with the followingstructure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀Co₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/Mg4/Hf3/PIT/IAO/Cu3/Fe₂₅Co₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.In this embodiment, a first Hf layer is deposited on a lower Cu spacerfollowed by deposition of a Mg layer and then a second Hf layer beforethe PIT/IAO sequence is performed. An upper Cu spacer is deposited onthe resulting CCP layer before the free layer is formed. In the twoA/X/A/PIT/IAO examples, the amorphous like Hf/Al/Hf or Hf/Mg/Hf trilayerconfiguration is treated with a PIT/IAO process sequence. Since thegrain size is further decreased in the CCP forming layer compared withthe A/X/PIT/IAO embodiment, more uniform oxidation and better uniformitycan be realized.

In another example that represents an A/PIT/IAO CCP scheme, a CCP-CPPGMR sensor (BTF3C6) was formed with the following structure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀Co₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀CO₃₀18/Cu5.2/Hf8/PIT/IAO/Cu3/Fe₂₅Co₇₅12/CoFeB10/Ni₉₀Fe₁₀35/R10/Ta60/Ru30.In this embodiment, a Hf layer is treated with the PIT/IAO sequencewithout an overlying Al or AlCu layer. Since Hf is amorphous, theoxidation will be more uniform from the top surface and via the grainboundary than when an A/X/PIT/IAO scheme is employed. Therefore, betteruniformity can be realized.

In an example that represents an A/PIT/IAO/A/PIT/IAO CCP schemeaccording to the present invention, a CCP-CPP GMR sensor was formed withthe following structure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₁₀Co₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/PIT/IAO/Hf3/PIT/IAO/Cu3/Fe₂₅Co₇₀12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.A first amorphous Hf layer is deposited on the lower Cu spacer and istreated with a PIT/IAO sequence to give a hafnium oxide template with Cumetal paths therein before a second amorphous Hf layer is deposited onthe first hafnium oxide template and a second PIT/IAO sequence isperformed to generate a second hafnium oxide template with Cu pathstherein. In effect, the A/PIT/IAO/A/PIT/IAO scheme represents a doublenano-oxidation layer (NOL) process. The first and second amorphoushafnium layers replace the Al or AlCu layer in a conventional CCPdesign. Since both amorphous hafnium layers were subjected to thePIT/IAO processes, the amorphous nature of the Hf layer results in amore uniform oxidation from the top surface and via the grainboundaries. Therefore better uniformity can be realized.

A modification of the previous sample that represents anA/PIT/IAO/Cu/A/PIT/IAO CCP scheme according to one embodiment of thepresent invention is shown in the following structure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀CO₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/PIT/IAO/Cu/Hf3/PIT/IAO/Cu3/Fe₂₅CO₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.The thin Cu layer formed on the first hafnium oxide template is believedto form a more uniform concentration of Cu metal paths in the resultingCCP layer and thereby improves uniformity.

In yet another modification of the A/PIT/IAO CCP scheme, a thin Cu layeris inserted between two A layers prior to performing the PIT/IAOsequence. For example, a first Hf layer, a thin Cu layer, and a secondHf layer are sequentially deposited on a lower Cu spacer before applyingthe PIT/IAO process steps. A structure formed according to anA/Cu/A/PIT/IAO embodiment of the present invention is represented by thestructure:Ta10/Ru20/IrMn70/Fe₁₀Co₉₀12/Fe₇₀CO₃₀17/Fe₁₀Co₉₀24/Ru7.5/Fe₇₀Co₃₀18/Cu2/Fe₇₀Co₃₀18/Cu5.2/Hf3/Cu2/Hf3/PIT/IAO/Cu3/Fe₂₅Co₇₅12/CoFeB10/Ni₉₀Fe₁₀35/Ru10/Ta60/Ru30.The thin Cu layer formed between the two amorphous hafnium layers isbelieved to form a more uniform concentration of Cu metal paths in theresulting CCP layer and thereby improves uniformity.

While this invention has been particularly shown and described withreference to, the preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of this invention.

1. A magnetic sensor structure comprised of a pinned layer, free layer,and a confining current path (CCP) spacer formed between the pinned andfree layers wherein the CCP spacer comprises: (a) a first copper layerformed on the pinned layer; (b) a spacer formed between the first copperlayer and a second copper layer, comprising: (1) a first metal oxidetemplate comprised of an oxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or B oranother amorphous metal or amorphous alloy, wherein the at-least onefirst metal oxide template has segregated Cu metal paths formed therein;and (2) at least a second metal oxide template which forms an interfacewith the first metal oxide template and is comprised of an oxide of ametal or metal alloy with segregated Cu metal paths formed therein; and(c) the second copper layer formed on a top surface of the first metaloxide template or the at least second metal oxide template, said secondcopper layer contacts said free layer.
 2. The magnetic sensor structureof claim 1 wherein the first metal oxide template has a thicknessbetween about 2 and 15 Angstroms and contacts said first Cu layer, and athe at least second metal oxide template contacts the second Cu layerand is comprised of an oxide of Al, AlCu, Mg, MgCu, Ti, Cr, Zr, Ta, Hf,or Fe and has a thickness from about 2 to 15 Angstroms.
 3. The magneticsensor structure of claim 1 wherein the spacer is comprised of two metaloxide templates said first metal oxide template and a second metal oxidetemplate are each made of an oxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or Bhaving Cu metal paths therein and with a thickness between about 2 and15 Angstroms and said first metal oxide template is comprised of adifferent metal than in the second metal oxide template.
 4. The magneticsensor structure of claim 1 wherein the spacer between the first andsecond copper layers is comprised of: (a) a first metal oxide templatemade of an oxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or B having segregated Cumetal paths therein and with a thickness between about 1 and 15Angstroms that contacts said first Cu layer; (b) a second metal oxidetemplate formed on the first metal oxide template and that is comprisedof an oxide of Al, AlCu, Mg, MgCu, Ti, Cr, Zr, Ta, Hf, or Fe havingsegregated Cu metal paths formed therein, said second metal oxidetemplate has a thickness from about 1 to 15 Angstroms; and (c) a thirdmetal oxide template made of an oxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or Bhaving segregated Cu metal paths therein and with a thickness betweenabout 1 and 15 Angstroms that contacts said second Cu layer and whereinsaid third metal oxide template is made of the same metal oxide as inthe first metal oxide template.
 5. The magnetic sensor structure ofclaim 1 wherein the spacer formed between the first and second copperlayers is comprised of: (a) a first metal oxide template made of anoxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or B having segregated Cu metalpaths therein and with a thickness between about 1 and 15 Angstroms thatcontacts said first Cu layer; (b) a second metal oxide template formedon the first metal oxide template and is comprised of an oxide of Al,AlCu, Mg, MgCu, Ti, Cr, Zr, Ta, Hf, or Fe having segregated Cu metalpaths formed therein, said second metal oxide template has a thicknessfrom about 1 to 15 Angstroms; and (c) a third metal oxide template madeof an oxide of Hf, Zr, CoFeB, Ta, Nb, Ti, or B having segregated Cumetal paths therein and with a thickness between about 1 and 15Angstroms that contacts said second Cu layer and wherein said thirdmetal oxide template is made of a different metal oxide than in thefirst metal oxide template.
 6. The magnetic sensor structure of claim 1wherein the first copper layer has a thickness from 0 to about 10Angstroms and the second copper layer has a thickness from 0 to about 10Angstroms.
 7. The magnetic sensor structure of claim 1 wherein the firstmetal oxide template has a thickness between about 2 and 15 Angstromsand contacts said second Cu layer, and the at least second metal oxidetemplate contacts the first Cu layer and is comprised of an oxide of Al,AlCu, Mg, MgCu, Ti, Cr, Zr, Ta, Hf, or Fe, and has a thickness fromabout 2 to 15 Angstroms.